This invention relates to improvements in moveable deflector rudders associated with propeller nozzles or ducts through which a liquid is accelerated for propulsion purposes.
The art discloses that the wetted surface area of such deflector rudders may be reduced when acted upon by the high velocity discharge from such a nozzle or duct without impairing the effectiveness of directional control, thereby reducing frictional losses and improving efficiency.
A plurality of such deflector rudders may be mounted vertically on a common transverse axis parallel to the plane end face of a nozzle or duct exit when they are commonly known as shutter rudders. The art discloses the use of such rudders in association with nozzles characterised by entry and exit terminations each comprising a single plane normal to the duct axis with rudders pivoted on a common axis parallel to the exit termination of the nozzle such that the propeller race divides to pass either side of said rudders thereby developing a pressure differential to provide a steering force.
Prior art also discloses the use of pivoted steering nozzles capable of rotation about a vertical axis whereby the nozzle discharge may be diverted to port or starboard as required to develop a steering force with, or without, the use of fixed or moveable vanes mounted on the nozzle.
Fixed nozzles with shutter rudders as known in the art are claimed to develop helm angles up to a maximum of 60.degree. port or starboard by the use of three or more such rudders. It is a purpose of the present invention to so harness the discharge from a fixed nozzle or duct to develop helm angles to 90.degree. and when used with a pivoted steering nozzle to have a capability of developing a reverse thrust.
The invention may also be applied to the leading termination of a nozzle or duct to improve directional control when going astern.
The following description is confined to two embodiments which typify the principles applicable to this invention, but it is to be understood that the invention is capable of modification and change and includes other details of construction without departing from the scope thereof.